Transmissions for motor vehicles are designed among others as so-termed dual-clutch transmissions, in which, in each case, an input shaft is associated with a partial transmission and in which the input shafts of the two partial transmissions can be connected by way of a respective powershift element to a drive input, for example an internal combustion engine or an electric machine, wherein the two powershift elements are combined in the form of a dual clutch. The gears that can be obtained by means of such a transmission are then distributed in alternation between the two partial transmissions so that, for example, one partial transmission is used to obtain the even-numbered gears and the corresponding other partial transmission the odd-numbered gears. It is also known to obtain the individual gears by means of one or more wheel stages or wheel planes, each having a different transmission ratio. By means of corresponding shifting elements these can be connected into the force or torque flow between the drive input and the drive output, so that a corresponding, desired transmission ratio between the drive input and the drive output can in each case be obtained.
By virtue of an alternating distribution of the gears between the two partial transmissions it is possible, when driving in a gear associated with one partial transmission, already to pre-select a subsequent gear by appropriate actuation of the shifting devices so that an eventual shift to the subsequent gear is enabled by opening the powershift element of the one partial transmission and shortly thereafter closing the powershift element of the other partial transmission. In this way the gears or gear steps of the transmission can be powershifted, which improves the accelerating ability of the motor vehicle by virtue of a gearshift that is consequently essentially free from traction force interruption, and which makes for more comfortable shifting processes for a vehicle driver.
Such dual-clutch transmissions can also be made with a countershaft assembly provided in addition to the drive input and the drive output, such that a more compact structure in the axial direction is made possible.
From DE 10 2005 044 068 A1 a transmission for a motor vehicle in the form of a dual-clutch transmission is already known. This powershiftable group transmission provides a large number of gears and is particularly suitable for commercial vehicles. A splitter group, a direct gear, a main group and a hollow shaft on a countershaft are provided. Between gears obtained by a change of the input constants within the splitter group without changing the transmission ratio in the main group, gearshifts can be carried out without traction force interruption. In addition, between two adjacent gears obtained by a transmission ratio change in the main group, again gearshifts can be carried out without traction force interruption.
From DE 10 2010 030 569 A1 a further transmission, particularly one for a motor vehicle with a hybrid drive, has become known.